And the news is breaking fast on that manhunt in boston. Just now, the order to stay indoors has been lifted for the residents there. But they are told to be watchful, because the search continues for a dangerous suspect. A long day becoming a long night. That one suspect is still on the loose, considered armed and extremely dangerous. His older brother is dead. And now, abc's chief investigative correspondent brian ross tells us where the investigation stands at this moment. Brian? Reporter: Well, diane, he got away. Officials conceded tonight they could not find him in watertown and they could no longer keep the entire boston area lockdown. So, now, a very dangerous man remains on the run even if he's only on foot. Military helicopters flew overhead. More than 1,000 police and naonal guardsmen swarmed the area. And there was fear of more violence. There is still a very, very dangerous individual at large. Reporter: It was only about 24 hours ago that the fbi first produced the surveillance videos that identified the suspected bomb bombers. Suspect one, 26-year-old tamerlan tsarnaev, who spent six months in russia last year. And suspect two, his younger brother, 19-year-old dzhokhar, a college student who became a u.S. Citizens just last year. We consider them to be armed and extremely dangerous, no one should approach them or apprehend them expect law enforcement. Reporter: It was no exaggeration. Just two hours later, around 7:30 p.M. Last night, officials say they got a tip the two were at this convenience store in cambridge. In short order, police reviewed the store's surveillance tape and concluded it was suspect two dzhokhar. Within an hour police say the two brothers then ambushed and killed a campus police officer and the m. I.T. Campus, 26-year-old sean collier. Next, the two men carjacked a mercedes suv, briefly kidnapped the driver and led police on a wild, violent chase through the streets of neighboring watertown. With the two men firing weapons and tossing explosives from the car. There's definitely hand grenades and automatic gunfire. In the exchange of the gunfire, we believe one of the suspects was struck and ultima ultimately taken into custody. Reporter: The older brother was hit with more than a dozen bullets and later died from his wounds. But dzhokhar, the younger, slipped away in the confusion and the darkness, triggering a massive manhunt for a very dangerous man. We believe this to be a terrorist. We believe this to be a man who has come here to kill people. We need to get him in custody. Reporter: Today, the fbi raided the brothers' apartment in cambridge, took two women into custody, and police ord more than 1 million people across the boston area to stay inside with their doors locked as the search for suspect number two continues. It is important that folks remain indoors and not open the door. Keep the doors locked. Reporter: But by the end of the day, still, no capture. Not even a sighting of a young man who authorities say is a cold blooded killer. And now, with darkness coming, diane, the search will be all that much more difficult. Authorities say the hope is that perhaps he was injured i yesterday's gun fight and have a hard time getting very far.

This transcript has been automatically generated and may not be 100% accurate.